Earth and space science Formation of the Universe
Big Bang Theory • We know the universe is expanding. • Astrophysicists have been able to work backwards to determine the starting point of the universe and roughly how long ago it was formed. • It makes sense to assume the universe was once closer together. • The Big Bang Theory is the most widely accepted theory. • About 15-20 billion years ago, some event occurred that created the universe and all matter in it. • No atoms or galaxies existed at time zero.
History of the big bang • Georges LeMaitre proposed the first workings of the Big Bang in the 1930’s. • George Gamow extended this theory in the 1950’s and 1960’s. • In the 1960’s Arno Penzias and Robert Wilson discovered radiation in space left over from the Big Bang. • This microwave radiation is called background radiation.
Stages of the big bang • Stage 1: Planck Time = 10-43 seconds, the temperature of the Universe is 1032 oC and only energyexisted. • Stage 2: Rapid expansion cools the Universe, particles slow down and attract because of gravity. (Quarks and leptons formed). • Stage 3: Matter has cooled enough to allow protons (hydrogen nuclei) to form. Neutrons also form. (10-4 s)
Stages of the big bang • Stage 4: After 3 minutes, the universe has cooled to 10 million degrees Celsius. Helium nuclei can bemade as neutrons and protons attract. • Stage 5: Cooling has now stopped the conditions needed for helium to form (one hour) • Stage 6: In half a million years, the universe has cooled to 3000 oC. Electrons now combine with nuclei to form atoms. They are now electrically neutral. • Stage 7: After 1 billion years, gravity forms the first stars and galaxies.
Quasars • Quasi-stellar radio sources – exist deep in space and emit huge amounts of radiation. • It is believed they exist at the very edge of the universe and may be the result of colliding galaxies 12 billion years ago. • The James Webb telescope should reveal more information on these objects.
Missing mass • The total observable mass of the universe is too low to explain why galaxies cluster together and the expansion rate of the Universe. • Dark matter and dark energy is the leading theory to account for this. • Neutrinos, string theory, dark stars and other theories exist, but dark matter is the leading theory.